Nutrients Contents And Microbial Activities Of Canopy Humus In Lithocarpus Xylocarpus Forest In Ailao Mountains, Yunnan, China

There are considerable amounts of canopy humus within the crowns of trees in tropical, subtropical and temperate montane moist forests. As an important structural component, the canopy humus provides essential substrates and nutrients for the growth of abundant epiphytes. In this study, the physical and chemical properties, microbial biomass and enzyme activities of humus from both canopy and forest floor were analyzed in a subtropical montane moist evergreen broad-leaved forest in Ailao Mts., Yunnan. The significant differences in the physical and chemical properties and microbial activities were found between the canopy humus and humus from forest floor, due to differences in origins, composition of humus and spatial distribution patterns.1. The canopy humus is an important nutrients pool in subtropical montane moist evergreen broad-leaved forest in Ailao Mts., Yunnan. It had lower pH value, and higher concentration of organic C, total N, total Ca, as well as C/N ratio and cation exchange capacity than humus under the forest floor. The concentrations of total K and total Mg were lower in the former than the latter. There was no significant difference in total P concentration between two humus types.2. The microbial biomass C and N, respiration rate were significantly higher in canopy humus than the humus under forest floor. The microbial biomass C and N in the canopy humus had 2.4 and 2.1 times more contents than humus under the forest floor, during 20 days incubation, respiration rate of canopy humus was always higher than humus under forest floor and showed stronger sustainable microbial activity. 3. Activities of sucrase, urease and protease were significantly greater in the canopy humus than its terrestrial counterpart. So we can study canopy humus using soil method.These results above indicated that the canopy humus belong to a category of organic histosol with high nutrients content and microbial activities, and thus it could play important roles in nutrients cycling, maintenance of species diversity pattern of epiphytes in the montane moist evergreen broad-leaved forest ecosystems.